Source : Webster's Revised Unabridged Dictionary (1913)

Republic \Re*pub"lic\ (r?-p?b"l?k), n. [F. r['e]publique, L.
   respublica commonwealth; res a thing, an affair + publicus,
   publica, public. See {Real}, a., and {Public}.]
   1. Common weal. [Obs.] --B. Jonson.

   2. A state in which the sovereign power resides in the whole
      body of the people, and is exercised by representatives
      elected by them; a commonwealth. Cf. {Democracy}, 2.

   Note: In some ancient states called republics the sovereign
         power was exercised by an hereditary aristocracy or a
         privileged few, constituting a government now
         distinctively called an aristocracy. In some there was
         a division of authority between an aristocracy and the
         whole body of the people except slaves. No existing
         republic recognizes an exclusive privilege of any class
         to govern, or tolerates the institution of slavery.

   {Republic of letters}, The collective body of literary or
      learned men.

Source : WordNet®

republic
     n 1: a political system in which the supreme power lies in a body
          of citizens who can elect people to represent them [syn:
           {democracy}, {commonwealth}] [ant: {autocracy}]
     2: a form of government whose head of state is not a monarch;
        "the head of state in a republic is usually a president"